<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>9-元素的层级关系</title>
    <style>
        div{
            width: 200px;
            height: 200px;
        }
        div:nth-of-type(1){
            width: 220px;
            background: red;
            position: absolute;
            left: 30px;
            top:50px;
        }
        div:nth-of-type(2){
            width: 240px;
            background: blue;
            float: left;
        }
        div:nth-of-type(3){
            width: 260px;
            background: orange;
        }
    </style>
</head>
<body>
    <!-- 
        层级：标准流 < 浮动 < 定位
     -->
    <div>西安</div>
    <div>厦门</div>
    <div>上海</div>
</body>
</html>